Supramolecular scaffold–directed two-dimensional assembly of pentacene into a configuration to facilitate singlet fission

Abstract

Molecular assemblies featuring two-dimensionality have attracted increasing attention, whereas such structures are difficult to construct simply relying on spontaneous molecular assembly. Here, we present two-dimensional assemblies of acene chromophores achieved using a tripodal triptycene supramolecular scaffold, which have been shown to exhibit a strong ability to assemble molecular and polymer motifs two-dimensionally. We designed pentacene and anthracene derivatives sandwiched by two triptycene units. These compounds assemble into expected two-dimensional structures, with the pentacene chromophores having both sufficient overlap to cause singlet fission and space for conformational change to facilitate the dissociation of a triplet pair into free triplets, which is not the case for the anthracene analog. Detailed spectroscopic analysis revealed that the pentacene chromophore in the assembly undergoes singlet fission with a quantum yield of 88 ± 5%, giving rise to triplet pairs, from which free triplets are efficiently generated (Φ T = 130 ± 8.8%). This demonstrates the utility of the triptycene-based scaffold to design functional π-electronic molecular assemblies.